fixinc: don't "fix" machine names in __has_include(...) [PR91085]

fixincludes/

	PR other/91085
	* fixfixes.c (check_has_inc): New static function.
	  (machine_name_fix): Don't replace header names in
	  __has_include(...).
	* inclhack.def (machine_name): Adjust test.
	* tests/base/testing.h: Update.